Lifting bridge



Dec. 1, B'REITWIESER V LIFTING BRIDGE Filed Feb: 20, 1935 JAVA AW /&V

INVEVNTOR Hf/NRICH BAEITA/IISEP x BYW ATTORNEY Patented Dec. 1, 1936 UNITED STATES LIFTING BRIDGE Heinrich Breitwieser, Griesheim, near Darmstadt,

Germany, assignor to Maschinenfabrik Augsburg-Nuernberg A. G., Nuremberg, Germany, a corporation of Germany Application February 20, 1935, Serial No. 7,331 In Germany February 22, 1934 4 Claims.

My invention relates to lifting and similar bridges, and the present invention has for its object an improvement in the rack-bar type of bridge lifting and lowering mechanism.

In lifting bridges in which the weight of the bridge is balanced by counter-poises suspended on cables passing over pulleys provided in the tops of the bridge towers use is made of endless articulated rack-bars or chains passing over cogor sprocket wheels supported both in the tops of the bridge towers and at the bottoms thereof. The upper cogor sprocket-wheels are used as driving wheels. Elongations of the cables from which the counterpoises are suspended cannot then affect the position of the bridge and its operating gear.

vHowever, experience has shown that the sudden standstill of the bridge, as its end bearings become seated on their supports, results in an excessive strain on the articulated rack-bars or chains.

To avoid any excessive strains on the rackbars, I support the cogor sprocket wheels provided at the bottoms of the bridge-towers by elastic or yielding members so that a certain backlash can take place as the end bearings of the bridge come in contact with their supports.

However, it is apparent that because of the continual increase in weight on the bridge side and the continual decrease in weight on the land side while the bridge is being lowered to its operative position, the movement of the bridge and the operating gear will be considerably accelerated, and the greater the acceleration, the greater will be the force with which the end bearings come to rest on their respective supports and the greater also will be the inertia of the operating gear. In order to prevent this undesirable acceleration of the movement of the bridge, the endless chain or articulated rack-bar over a certain stretch of its length is made heavier. When the bridge is in its inoperative position (broken-line position), the heavier portion of the chain or rack-bar is on the bridge side, but as the bridge is being lowered to its operative position (full-line position) the heavier portion of the chain or rack-bar moves toward the land side so that the changes in weight in the cables carrying the counterpoises are continually compensated. When the bridge has reached its operative position, the heavier portion of the chain or rack-bar assumes the position shown in the drawing.

An embodiment of my invention is, by way of illustration, diagrammatically shown on the appended drawing, on which appear in side elevation one of the bridge towers, one of the endless articulated rack-bars, one of the cables with the counterpoise suspended therefrom, and a H fragment of the bridge, both in its operative position :(full lines) and in its inoperative position (broken lines).

In the drawing, a denotes the bridge and. b one of the cables from which the bridge is sus- Y pended. c is the pulley, over which the cable 0 passes, and d the couri'terpoise suspended from the free end of the cable. e denotes the endless articulated rack-bar which passes in free loops over two cog-wheels, one of which is shown at g rotatably mounted in the top of the tower 1, while the other is shown at'h rotatably mounted in the bottom of the tower. A similar arrangement is provided in the otherbridge-tower (not shown). I

For each bridge end there are, of course, pro- 20 vided two articulated rack-bars, two'cables, two pulleys, two cog-wheels g and two cog-wheels h. The uppercog-wheels g are mounted on a horizontal shaft. At 2' is shown-a counter-shaft disposed parallel with theshaft-of the cog-wheels g and carrying two smaller cog-wheels which mesh with the larger cog-wheels g. The shaft 2 may be rotated from any suitable source of power (not shown).

As shown, the cog-wheels h at the bottom of 30 the tower f are suspended from helical tension springs l fastened to lugs is projecting from suitable portions of the tower.

The endless articulated rack-bar e as shown in the drawing is composed of articulated links but with the major portion of the rear run composed of links larger than those of the remaining portion of the rack-bar to make it understood that the portion of the rack-bar comprising the larger links is heavier so as to be able to compensate the weight of either the front or rear run of the rack-bar for the above mentioned purpose.

When the cog-wheels g are rotated in counterclockwise direction as shown by the arrow in the drawing, the bridge a is lifted from its full-line or operative position until it assumes the brokenline or inoperative position. Thereafter, when the cog-wheels g are rotated in the opposite direction, the bridge will be lowered. When the end bearings 0f the bridge come to be seated on their respective support, the operating gear, because of the inertia tends to continue its movement resulting in a pull on the articulated rackbar, so that also the lower cog-wheels (h) have the tendency to 'further rotate. If these cogwheels were mounted in a fixed position, they could not continue to rotate, because the rackbar is held fast on the bridge side by the seated bridge. Consequently, the links of the rack-bar would be subjected to heavy shocks, but because of the elastic or yielding mounting'of the lower cog-wheels (h), these shocks are either completely avoided or at least very materially decreased, because the elastic mounting of the cog wheels (h) permits a further rotation of the same upwards against the tension of the spring Z. Because of the cOmpleteYcOmpensation ofv the weights, the descent of the bridge takes place entirely uniformly, and because of the yielding or elastic suspension of the lower cog-wheels the backlash thereby rendered possible allows the movement of the operating parts to'be continued to a certain extent, after the end bearings of the bridge come in contact with their respective supports, so that all undue or excessive strains on the operating parts are completely avoided.

I claim:

1.- A lifting device for lift bridges and the like having counterpoises suspended from cables or the like, comprising a driving gear separated from the means for holding said cables, and endless articulated rack-bars or chains conducted over upper and lower cog-wheels or chainwheels supported in the towers pertaining to the bridge, said upper wheels serving as driving wheels for said gearing, said device comprising, in combination with the above-stated members, yielding members at which the lower of the said wheels are supported and which are adapted to permit an elastic backlash of the gearing when the-bridge bearings contact with the supports provided for them.

2. A lifting device for lift bridges and the like, comprising, in combination with the bridge proper, and with bridge towers at which the bridge proper can be vertically moved, cables from which the bridge proper is suspended, pulleys holding said cables, counterpoises at the free ends of said cables, endless vertical articulated rack-bars or chains connected with the bridge proper, cog-wheels or chain wheels guiding said rack-bars or chains and being supported on and at said towers, and elastic intermediate members inserted between the lower of said wheels and the adjacent portions of the towers.

3. A lifting device for lift bridges and similar bridges having counterpoises suspended from wire cables or the like, comprising a driving gear separated from the means for holding said cables,

said device comprising, in combination with the members stated, endless vertical articulated rackbars or chains connected with the bridge and comprising each two' portions of different weights,

the heavier portion being located counter to the bridge when this'is in its lower position; cogwheels or chain-wheels guiding said rack bars or chains and being supported in the towers pertaining to the bridge, the upper of said wheels serving as driving members for said gearing, and elastic members at which the lower of the said wheels are supported and which are adapted to permit a'yielding backlash of the gearing when the: bridge bearings touch the supports provided for them.

. 4. A lifting device for lift bridges and similar bridges, comprising, in combination with the bridge proper and with towers at which the bridge proper can be vertically moved, cables from which the bridge proper is suspended, pulleys holding said cables, counterpoises at the free ends of said cables, endless vertical articulated rack-bars orchains connected with the bridge and comprising each two portions of different weights, the heavier portion being located counter to the bridge when this is in its lower position; cog-wheels or chain-wheels guiding said rack-bars or chains and being supported in the towers pertaining to the bridge, the upper of said wheels serving as driving members for said gearing, and elastic members at which the lower of the said wheels are supported and whichv are adaptedto permit a yielding backlash of the gearing when the bridge bearings touch the supports provided for them.

HEINRICH BREITWIESER. 

